Moparts

best shift point ?

Posted By: 68notch

best shift point ? - 12/29/10 01:23 AM

68 barracuca , 71 440 , 9.5 keith black , 509 purple , dual 4 wieland tunnel ram , 625 carters , 4 speed , 3.91 sure grip , msd 6 , 2 inch hooker fenderwell headers , 3 1/2 inch glasspacks , i am thinking 6000 for banging gears , too much for the stock bottom end ? or am i being parriniod , or should i let it wind to 7 ?
Posted By: Prince_Valiant

Re: best shift point ? - 12/29/10 01:29 AM

I would think ideally, yeah...6500 is the minimum that it would like. What kind of heads? What work has been done?

6500 should be okay for a stock bottom end...
Posted By: Pacnorthcuda

Re: best shift point ? - 12/29/10 01:48 AM

Quote:

I would think ideally, yeah...6500 is the minimum that it would like. What kind of heads? What work has been done?

6500 should be okay for a stock bottom end...




1000 over factory redline for many 440's? Stock bottom end. Pushing it.

I would say the best shift point would be 1/2 the RPM drop between gears, over the max hp point in the powerband--IF the bottom end it up to the task. Assuming max acceleration is the goal.
Now finding that point is the key.
Posted By: dennismopar73

Re: best shift point ? - 12/29/10 03:27 AM

6500 i dont shift my race car there
hell shift it at 7500 let er fly
hahah

can help but hink that ?? 5500 is really pushing it
Posted By: Sport440

Re: best shift point ? - 12/29/10 03:48 AM

While, that combo could still easily rev to 7000 rpm, Id keep it around 6000-6200 rpm for best ET and engine longjevity.

You wont get to many passes reving it to 7000 grand
Posted By: 68notch

Re: best shift point ? - 12/29/10 03:52 AM

Quote:

I would think ideally, yeah...6500 is the minimum that it would like. What kind of heads? What work has been done?

6500 should be okay for a stock bottom end...



stock 346 heads , as far as i know factory rebuild , it was done in 98 and hardly drove , according to what info i have
Posted By: Sport440

Re: best shift point ? - 12/29/10 04:16 AM

With those heads and cam 6000 rpm will be plenty.

With free flowing heads the 509 cam is done around 6200 rpm, but will rev higher. mike
Posted By: Prince_Valiant

Re: best shift point ? - 12/29/10 05:07 AM

Quote:

1000 over factory redline for many 440's? Stock bottom end. Pushing it.


For most factory type bottom ends, the max mean safe pistons speeds is around 4,500 ft/min...a bit lower if cast crank/pistons (3750)

Max safe rpm = (max mean piston speed x 6)/stroke length.

So, this for the range:
forged rods/pistons from factory
MSR= (4500 x 6)/3.75 = 7200rpm.

if cast crank piston/crank from factory
MSR= (3750 x 6)/3.75 = 6000rpm

Now, not knowing exactly what he's using for his short block or anything, I'm just assuming...but mopar didn't make junk. Good oiling, not too long a stroke, good cranks/rods/pistons typically...yep, not too worried about stating someone could probably get away with 6500rpm.

It's not the sharpest combo...it'd do a lot better with improved heads. Given the stock nature of the heads my guess is your power peak will actually occur under 6500rpm with what you've got. The heads are ultimately choking off it's potential which would seem to be up a bit higher still.

Of course, to reach the full potential, you'd really want a new short block with forged internals, and probably a girdle for the block, or at least top notch fasteners.
Posted By: 383man

Re: best shift point ? - 12/29/10 05:38 AM

I like to shift by the feel of the eng. When it seems to peak I shift. I can tell you I have a mild 906 headed 440 in my 63 right now with the MP .557 cam. It feels like 6200 is the happy spot. Thats where I shift it at and it traps about 6300 to 6400. Ron
Posted By: 68notch

Re: best shift point ? - 12/29/10 06:04 AM

thanks very much , another question if i may , if im going for better heads in the future , should i think about beefing up the bottom first ?
Posted By: StealthWedge67

Re: best shift point ? - 12/29/10 08:13 AM

Yes, Yes, & Yes. If it breaks, it's liable to take a lot of parts with it. If a rod lets loose @ 6k, you could easily find yourself salvaging only the headers and intake..... literally. Build the foundation before you start on the second story.
Posted By: GTX MATT

Re: best shift point ? - 12/29/10 08:41 AM

Quote:

While, that combo could still easily rev to 7000 rpm, Id keep it around 6000-6200 rpm for best ET and engine longjevity.

You wont get to many passes reving it to 7000 grand




I would think that too but I have a buddy that bought a '67 GTX brand new and installed a 325 degree Isky cam in it with fenderwell headers and 4.56s. Although I doubt it produced best ETs he dumped the clutch at 7200 (on slicks) and shifted it at 7000, beating the car all the time and running it probably twice a month at the strip for two years.

How it held up I dont know but he traded it in for a Dart GTS in '69 and while it was still on the dealership lot the Dana blew up, no doubt from the abuse he had put it through. That being said I dont push my stock bottom end 440 past 5000.
Posted By: DaytonaTurbo

Re: best shift point ? - 12/29/10 09:27 AM

I'd push it to 6000. With those stock heads I don't think there'd be any gain to taking it higher.
Posted By: Anonymous

Post deleted by moparts - 12/29/10 05:01 PM

Posted By: pressureangle

Re: best shift point ? - 12/29/10 05:34 PM

Stock heads aren't the best combo to put under a tunnel ram and 2" headers. My WAG is that about 6k will be your shift point, but it may be 500 RPM either side of that. Let your time slips be your guide. 60ft time will give your best launch RPM, and 1/4 mile MPH will give best shift RPM.

If the motor has no modifications to the oiling system, RPM over 5500 risks starving the rod bearings.
Posted By: 68notch

Re: best shift point ? - 12/29/10 06:42 PM

Quote:

I agree with the above answer since it's reason is very simple. Many folks said 6000 and I believe that as well. There is no reason to take it to 7200 like this: (my brother in law mr5speed)
http://video.google.com/videoplay?docid=7528903995676743423&hl=en




holy !!! what i wouldn't give to be able to shift gears like that , ive got some practicing to do
Posted By: 68notch

Re: best shift point ? - 12/29/10 06:54 PM

Quote:

Stock heads aren't the best combo to put under a tunnel ram and 2" headers. My WAG is that about 6k will be your shift point, but it may be 500 RPM either side of that. Let your time slips be your guide. 60ft time will give your best launch RPM, and 1/4 mile MPH will give best shift RPM.

If the motor has no modifications to the oiling system, RPM over 5500 risks starving the rod bearings.




i had the tunnel ram , thats why it went on and it looks just too cool to take off . i went with the bigger headers so that if i update the heads i can still use them , ive tried to put a picture on and cut it down the size of a postage stamp and its still too big so youll just have to take my word lol
Posted By: Mr.Yuck

Re: best shift point ? - 12/29/10 07:00 PM

Shift where you feel it's best. With stock heads I'd guess you'll be maxed out around 6000-6200. I had a 509'd 383 w/ ported 915 2.14/1.81 valves. Friend asks what are you shifting at? I said 6800, he's like whooo dude whay to high try 62-6500. did and it slowed the car down. Drive it you'll know where the power drops off. I pulled 3rd one time at 7200, helped me win by a 1/2 fender against at Chevy II in the finals.
Posted By: sixpackgut

Re: best shift point ? - 12/29/10 09:58 PM

old timer would jump in some guys 440 powered car and shift at 5500 and get a new best in the other guys car. over and over this would happen. i heard him tell this story so i tried it, my car was a 493 but i was spinning around 6500. ET didnt change much but my mph went up shifting at 5800.

about a year ago, in the race section, a guy got a new best with a 440 shifting it at 5200. most guys would never even try that so they would never find out
Posted By: RTDaddy

Re: best shift point ? - 12/29/10 10:23 PM

Carowner: "How do you know when to shift?"
Reply: "When it feels like the floorboards getting ready to lift"

You can usually feel the car start to nose over, it's time.

"IF YOU'RE UNDER CONTROL, YOU AIN'T GOING FAST ENOUGH."
Posted By: 68notch

Re: best shift point ? - 12/29/10 11:24 PM

Quote:

Carowner: "How do you know when to shift?"
Reply: "When it feels like the floorboards getting ready to lift"

You can usually feel the car start to nose over, it's time.

"IF YOU'RE UNDER CONTROL, YOU AIN'T GOING FAST ENOUGH."



Posted By: DaveRS23

Re: best shift point ? - 12/30/10 02:31 AM

My personal experience with more or less stock bottom ends has been that a 6,000 RPM shift point is kinda the dividing line. The farther under 6,000 I keep them, the less troubles I have. The more often that I approach and pass 6,000, the problems come more often.

And on my engines, the power drops off fast in the high 5,000s with stockish heads.

Posted By: Dadrules

Re: best shift point ? - 12/30/10 05:13 AM

Quote:

Quote:

I agree with the above answer since it's reason is very simple. Many folks said 6000 and I believe that as well. There is no reason to take it to 7200 like this: (my brother in law mr5speed)
http://video.google.com/videoplay?docid=7528903995676743423&hl=en




holy !!! what i wouldn't give to be able to shift gears like that , ive got some practicing to do




amen. I'm about to begin bracket racing at the ripe old age of 61 with a 65 barracuda small block we've been working on way too long. I loved that video.. thanks!
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